Removal of methylene blue and crystal violet from aqueous solutions by palm kernel fiber

The ability of palm kernel fiber (PKF) to adsorb methylene blue (MB) and crystal violet (CV) from aqueous solutions has been studied. Adsorption studies were carried out at different initial dye concentrations (20, 40. 80 and 160 mg/L), contact time, pH (1.0-11.0) and sorbent doses (0.4, 2.0, 4.0 and 8.0 g/L). Other factors affecting the absorption process as stirring rate, ionic strength and temperature of the initial dye solution were also examined. Adsorption data were modeled using Langmuir. Freundlich and Temkin adsorption isotherms. Equilibrium data of the biosorption process fitted very well to the Freundlich model (R-2 = 0.997 and 0.991 for MB and CV, respectively). The thermodynamic parameters such as Delta H degrees, Delta S degrees and Delta G degrees were evaluated. The dye adsorption process was found to be endothermic for the two dyes. The maximum adsorption capacity Q(o) was 95.4 mg/g for MB and 78.9 mg/g for CV at an optimum pH. Adsorption kinetic was verified by pseudo-first-order and pseudo-second-order models. The results indicated that the dye uptake process followed the pseudo second-order and saturation type rate expressions for each dye. (C) 2011 Elsevier B.V. All rights reserved.